1. Field of the Invention
The present invention relates to an optical transmitter, an operation controlling method for the same, and a recording medium, and more particularly, to a method for adjusting light output power during switching of the wavelength of a variable-wavelength light source having variable output wavelength.
2. Description of the Related Art
FIG. 3 shows the configuration of an optical transmitter of a related art. In FIG. 3, the optical transmitter includes a Continuous Wave-Laser Diode (CW-LD) unit 1 as a variable-wavelength light source, a modulator 2, a modulator driving unit 3, and a control unit 6.
The modulator driving unit 3 drives the modulator 2 in accordance with data to be transmitted, and the modulator 2 modulates light output from the CW-LD unit 1 and outputs the modulated output as an optical transmission signal. At normal times, a CW-LD control unit 61 of the control unit 6 controls the CW-LD unit 1 so that the light output power and output wavelength of the CW-LD unit 1 are optimized. At normal times, a modulator control unit 62 of the control unit 6 controls the modulator 2 so that the waveform of output light from the modulator 2 is optimized.
When the output wavelength of the CW-LD unit 1 is switched (varied), the CW-LD control unit 61 switches the output wavelength by varying the device temperature and LD bias current of the CW-LD unit 1 to make feedback control, while monitoring the light output power and output wavelength from back light output of the CW-LD unit 1 so that light output power characteristics do not degrade during wavelength switching for maintenance of transmission characteristics.
During switching of wavelength, the modulator control unit 62 controls the bias voltage of the modulator 2 to optimize the output waveform while monitoring the output light from the modulator 2 as at normal times. Wavelength switching of the CW-LD unit 1 is conducted when there is no data to transmit.
In switching of the output wavelength of the CW-LD unit 1, if priority is given to the speed of wavelength switching, light output power characteristics will degrade. However, when it is necessary for the CW-LD control unit 61 to make feedback control for wavelength switching so that light output power characteristics do not degrade as mentioned above, there will be problems of limitation on the time for wavelength switching due to conditions of time constants or the like for the feedback control and decrease in the speed of wavelength switching.
Japanese Patent Laid-Open No. 2002-049014 describes an optical transmitter that includes a light emitting device and an optical modulator, wherein the characteristics of the optical modulator are stored in ROM, and the driving current source of the light emitting device is controlled based on the information stored in the ROM to keep output of modulated light constant. However, Japanese Patent Laid-Open No. 2002-049014 includes no description on operations during wavelength switching.